Forsøksdyr: The Norwegian fjellrev captive-breeding programme – follow up of released individuals and their descendants

Godkjenningsdato 19.06.2018

The Arctic fox has been listed as critically endangered during the past decades in Norway and became a priority species in 2015. The captive-breeding programme aims at developing and refining captive-breeding and release into areas were the Arctic fox has become extinct or few in numbers. Since 2006, 364 pups have been released in selected mountain areas. Within a few years, the captive breeding programme has proven to be the most efficient conservation action and has managed to re-establish populations in Dovrefjell, Finse and Junkeren. The programme has also provided emigrants that strengthened small remnant populations elsewhere in Norway and Sweden. More than 700 wild-born pups have been registered as descendants from released captive-bred individuals.

The marking of captive-bred foxes and their wild-born offspring is essential to document the success of the programme and to enable adjustments of release methodologies, as well as compiling valuable data on population numbers, structure and distribution for adaptive management. It also provides valuable data input to associated and collaborative projects (National Arctic fox monitoring programme, Ecofunc, and projects with Stockholm University).

Herein we apply for annual capture, marking, and limited tissue sampling of up to 250 wild born pups and 20 adult arctic foxes. The prioritized areas for marking and close follow up are Dovrefjell and other active release areas in Norway. In addition, we are applying for the capture and marking of up to 50 adults in the winter in Dovrefjell to evaluate the effects of removing supplemental feeding. In total, we apply for 500 pups and 140 adults over two years. These totals have been determined by experience and a power analysis.

Animal handling will be carried out by experienced and trained personnel following protocols with instructions for capture, handling and den visits. The foxes are marked with a passive pit-tag (microchip) and it is not necessary to re-capture the individuals after the initial marking. Several pit-tag readers have been placed at selected sites (within food dispensers). These constitute the main source of relocation data, complemented by DNA data from marking and collected via scats by the National monitoring programme (helps recording dispersals into areas without pit-tag readers). The handling is minimized (max 15 minutes handling per individual) because the marking procedure only consists a few actions (pit-tag injection, weight, back leg length, DNA- sample, hair sample, and sexing). We therefore consider the procedure to cause light (pups) and up to moderate (adults) pain/discomfort to handled individuals and much less for other individuals at the den site. The protocol also implies minimized number of visits and days spent at each den site.

For winter captures, we have refined our protocol to include redused active trapping area and increased trap checks (two times daily) and have included collection of scats for DNA data to reduce the need for a large number of live captured animals. In addition, we have updated our traps to the newer models to lessen the potential for injury. We, therefore, expect up to moderate pain/discomfort in the trapped adults.